Stent manufacturing apparatus

ABSTRACT

An apparatus for imprinting a stent configuration image from a mask form onto a tubular stent blank. The stent blank has a longitudinal axis and a photosensitive coating on the outer surface thereof. The apparatus includes a journaling mechanism adapted to receive the stent blank, and operable to rotate the stent blank about its longitudinal axis; a radiation source operable to direct light at a first surface region of the stent blank when mounted in the journaling mechanism, to thereby expose the photosensitive coating on said first surface region of the stent blank; and a mask form movement mechanism configured to mount the mask form in the apparatus and to move the mask form along a path in which the mask form contacts the stent blank in said first surface region thereof along a concurrent convex arcuate segment.

PRIOR APPLICATIONS

[0001] This is a continuation of application Ser. No. 09/246,180, filedFeb. 2, 1999, allowed, which is a division of application Ser. No.08/835,015, filed Apr. 8, 1997, now U.S. Pat. No. 5902475, both of whichapplications are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

[0002] In general, the present invention relates to percutaneoustransluminal devices and methods which are used to treat obstructed(sclerotic) vessel lumina in humans. In particular, the presentinvention is an improved method for fabricating stents or prostheses. Inaddition, the improved method employs a novel apparatus.

BACKGROUND OF THE INVENTION

[0003] Cardiovascular disease is commonly accepted as being one of themost serious health risks facing our society today. Diseased andobstructed coronary arteries can restrict the flow of blood and causetissue ischemia and necrosis. While the exact etiology of scleroticcardiovascular disease is still in question, the treatment of narrowedcoronary arteries is more defined. Surgical construction of coronaryartery bypass grafts (CABG) is often the method of choice when there areseveral diseased segments in one or multiple arteries. Conventional openheart surgery is, of course, very invasive and traumatic for patientsundergoing such treatment. In many cases, less traumatic, alternativemethods are available for treating cardiovascular diseasepercutaneously. These alternate treatment methods generally employvarious types of balloons (angioplasty) or excising devices(atherectomy) to remodel or debulk diseased vessel segments. A furtheralternative treatment method involves percutaneous, intraluminalinstallation of one or more expandable, tubular stents or prostheses insclerotic lesions. Intraluminal endovascular prosthetic grafting is analternative to conventional vascular surgery. Intraluminal endovasculargrafting involves the percutaneous insertion into a blood vessel of atubular prosthetic graft and its delivery via a catheter to the desiredlocation within the vascular system. The alternative approach topercutaneous revascularization is the surgical placement of vein,artery, or other by-pass segments from the aorta onto the coronaryartery, requiring open heart surgery, and significant morbidity andmortality. Advantages of the percutaneous revascularization method overconventional vascular surgery include obviating the need for surgicallyexposing, removing, replacing, or by-passing the defective blood vessel,including heart-lung bypass, opening the chest, and general anesthesia.

[0004] Stents or prostheses are known in the art as implants whichfunction to maintain patency of a body lumen in humans and especially tosuch implants for use in blood vessels. They are typically formed of acylindrical metal mesh which can expand when pressure is internallyapplied. Alternatively, they can be formed of wire wrapped into acylindrical shape. The present invention relates to an improved methodof manufacturing stents.

[0005] Stents or prostheses can be used in a variety of tubularstructures in the body including, but not limited to, arteries andveins, ureters, common bile ducts, and the like. Stents are used toexpand a vascular lumen or to maintain its patency after angioplasty oratherectomy procedures, overlie an aortic dissecting aneurysm, tackdissections to the vessel wall, eliminate the risk of occlusion causedby flaps resulting from the intimal tears associated with primaryinterventional procedure, or prevent elastic recoil of the vessel.

[0006] Stents may be utilized after atherectomy, which excises plaque,or cutting balloon angioplasty, which scores the arterial wall prior todilatation, to maintain acute and long-term patency of the vessel.

[0007] Stents may be utilized in by-pass grafts as well, to maintainvessel patency. Stents can also be used to reinforce collapsingstructures in the respiratory, biliary, urological, and other tracts.

[0008] As described in U.S. Pat. No. 4,776,337 issued to Palmaz, thecylindrical metal mesh shape is produced by laser cutting a thin walledmetal tube. A laser is used to cut away all but the lines and curves ofthe mesh. The method of U.S. Pat. No. 4,776,337 is applicable forrelatively large mesh shapes and for meshes whose lines are relativelywide. However, for more delicate and/or intricate shapes, the spot sizeof the laser is too large.

[0009] European Patent Application EP 0 709 067 A2 describes a stentfabrication method of preparing a flat pattern design, cutting thepattern in the flat sheet, deforming the sheet to cause the edges totouch, connecting at least the edges at least one point usually by awelding process, and then polish the finished product. The disadvantageof this process is that flat sheet must be deformed to form the finaltubular configuration, and that there is a longitudinal attachment pointwhich provides a discontinuous outer contour and a potential weak pointfor failure. Furthermore, the weld is metallurgically and chemicallyunstable and will degrade in the human body. In addition, this processrequires several critical manufacturing steps which are eliminated bythe present invention.

[0010] U.S. Pat. Nos. 5,514,154 and 5,421,955 describe a stentmanufacturing process utilizing a computer controlled laser toselectively remove an etchant-resistant coating form a design resemblinga stent. The use of a laser to selectively remove the etchant-resistantcoating is a relatively expensive and complicated process. The lasermust be linked to a computer controlled X-Y movement system that mustprecisely control the rotation and movement of the laser for stentfabrication. Variances in this process will transcend into variabilityin the fabricated stent. The present invention neither requires the useof an expensive laser system nor the complex movement system.

[0011] It is, therefore, an object of the present invention to provide astent fabrication method which can produce stents with relativelyintricate, delicate and detailed designs from a tubular member whichnegates the disadvantages of the prior designs.

[0012] In addition, it is a further object of the present invention toprovide a method of fabricating a stent which involves processing atubular member whereby no connection points to join the edges of a flatpattern are necessary.

SUMMARY OF THE INVENTION

[0013] The present invention involves a method of fabricating a stent byprocessing a tubular member. During the fabrication process, a novelapparatus is employed to expose a coated tubular member to a precisepattern of UV light dictated by a specifically designed film which movesover the tubular member as it is rotated.

[0014] The method of manufacture includes the steps of firstelectro-cleaning the tubular member with an appropriate solution. Thetubular member comprises stainless steel, platinum, titanium, tantalum,gold alloy, or a gold/platinum alloy, but any number of metallicelements or polymeric materials can be employed.

[0015] Once the tubular member is cleansed of contaminates, the outersurface is uniformly coated with a photo-sensitive resist. Optionally, acoupling agent may be used to facilitate the bonding of thephoto-sensitive resist to the tubular member. The coupling agent is notessential in that some tubular member compositions bond directly to thephoto-sensitive resist solution without the need for a coupling agent.

[0016] This coated tubular member is then placed in an apparatusdesigned to rotate the tubular member while the coated tubular member isexposed to designated pattern, of ultraviolet (UV) light. The apparatuscontrols the exposure of the coated tubular member by utilizing aphotographic film with a specified computer generated imprintedconfiguration, transferring the UV light in the specified pattern to thecoated tubular member. The UV light activates the photo-sensitive resistcausing the areas where UV light is present to expose (cross-link) thephoto-sensitive resist. The photo-sensitive resist forms cross linkswhere is it exposed to the UV light thus forming a pattern of hardenedand cured polymer which mimics the particular stent design surrounded byuncured polymer. The film is adaptable to virtually an unlimited numberof intricate stent designs. The process from the apparatus results inthe tubular member having a discrete pattern of exposed photo-sensitivematerial with the remaining areas having unexposed photosensitiveresist.

[0017] The exposed tubular member is immersed in a negative resistdeveloper for a specified period of time. The developer removes therelatively soft, uncured photo-sensitive resist polymer and leavesbehind the cured photo-sensitive resist which mimics the stent pattern.Thereafter, excess developer is removed from the tubular member byrinsing with an appropriate solvent. At this time, the entire tubularmember is incubated for a specified period of time, allowing theremaining photo-sensitive resist polymer to fully cure (harden) andattach to the surface of the processed tubular member. The tubularmember can be incubated at room temperature or can be exposed to a heatsource in the range of 100 to 400 degrees Celsius.

[0018] The processed tubular member is then exposed to aelectro-chemical etching process which removes uncovered metal from thetubular member, resulting in final tubular member or stentconfiguration.

[0019] This process can lend itself to virtually an unlimited number ofstent designs and configurations. By modifying the film and employingthe identical process one can fabricate a variety of stent designs.

[0020] The present invention will be understood and appreciate morefully from the following detailed description taken in conjunction withthe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a flow chart illustration of the stent fabricationmethod of the present invention;

[0022]FIG. 2 is a schematic view of the finished stent of the presentinvention in its intended operational environment;

[0023]FIG. 3 is a schematic representation of the first cleaning step ofthe manufacturing process of the present invention;

[0024] FIGS. 4(A) and (B) are cross-sectional views of the tubularmember of the present invention with the optional coupling agent engagedto the outside surface of the tubular member;

[0025]FIG. 5A is a top view illustration of one frame of film with astent configuration imprinted on the film;

[0026]FIG. 5B is a slanted top view illustration of several frames on asheet of film with a stent configuration imprinted on each frame;

[0027]FIG. 6 is a side view illustration of the apparatus used tosimultaneously rotate the coated tubular member, advance the film, andexpose a portion of the outer surface of the tubular member to UV light;

[0028]FIG. 7 is a schematic representation of the processing step ofimmersing the coated tubular member to expose to UV light in a negativeresist developer to yield an unrefined stent;

[0029]FIG. 8 is a schematic representation of the processing step ofrinsing the excess negative resist developer from the unrefined stent;

[0030]FIG. 9 is a schematic representation of the processing step ofchemically or electrochemically treating the unrefined stent to afinished stent;

[0031]FIG. 10 is a perspective view of a stent resulting from themanufacturing process of the present invention;

[0032]FIG. 11 is a cross-sectional view of one configuration of theouter surface of a strut as seen along line 11-11 in FIG. 10 showing atrapezoidal protruding configuration that is directed radially from thelongitudinal axis of the stent as a result of the present inventionprocess;

[0033]FIG. 12 is a cross-sectional view of another configuration of theouter surface of a strut as seen along line 11-11 in FIG. 10 showing atriangular protruding configuration that is directed radially from thelongitudinal axis of the stent as a result of the present inventionprocess;

[0034]FIG. 13 is a cross-sectional view of another configuration of theouter surface of a strut as seen along line 11-11 in FIG. 10 showing aprotrusion with a radius that is directed radially from the longitudinalaxis of the stent as a result of the present invention process;

[0035]FIG. 14 is a perspective view of the apparatus used in the presentinvention stent fabrication process;

[0036]FIG. 15 is a cross-sectional view of the apparatus as seen alongline 2-2 in FIG. 14 showing the perspective view of the apparatus;

[0037]FIG. 16 is a cross-sectional view of the light source and theregulating platform;

[0038]FIG. 17 is a cross-sectional enlargement of the regulatingplatform of the apparatus; and

[0039]FIG. 18 is a perspective view of the regulating platform.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0040] Reference is now made to FIG. 1, which illustrates the stentfabrication method of the present invention.

[0041] In the stent fabrication method of the present invention, adrawing representing a stent is designed on a computer that generates aprintout with the desired stent pattern presented in a flat format 40.The pattern of step 40 can be printed on any size printout, butgenerally must be reduced to fit the requirements of photographic film42 and the dimensions of the desired stent design. After the drawing ofthe stent pattern is reduced, it is transferred onto a high contrasttransparent film 44. The final step requires that the photo-transparentfilm be calibrated to match the circumference and dimensions of thetubular member employed in the fabrication process 46.

[0042] The tubular member can be any type of biocompatible materials,such as titanium, tantalum, stainless steel, platinum, gold alloy orgold/platinum alloy, a polymeric material or a material which is platedwith a biocompatible material. The preferred candidate for stainlesssteel material for the tubular member is either the 316 or 321 stainlesssteel classes. The process of forming the tubular member is well knownextrusion technology. It is preferable to have the tubular memberrelatively consistent in diameter, concentricity, thickness andseamless.

[0043] To process the particular tubular member, is it preferable toclean and remove contaminates 20. The tubular member can be furthertreated by exposing the cleaned tubular member to a temperature in therange of 100 to 200 degrees Celsius. Dependent on the tubular member'smaterial and the photo-sensitive resist material employed, a couplingagent may be necessary to enhance the adhesion of the photo-sensitiveresist to the outer surface of the tubular member. Therefore, aftercleaning, the outside surface of the tubular member is optionally coatedwith a coupling agent 22. The processed tubular member is then coatedwith a photo-sensitive solution 24. Next, a novel apparatus is employedwhich exposes the resist coated tubular member to a specific pattern ofUV light 26. The exposed tubular member is then immersed into a negativeresist developer 28, whereby unexposed resist is removed from theprocessed tubular member.

[0044]FIG. 2 is a schematic view of the finished stent of the presentinvention in its intended operational environment. A stent resultingfrom the present invention can be used to treat atherosclerotic disease,prevent vessel recoil, overlie an aortic dissecting aneurysm, tackdissections to the vessel wall, and eliminate the risk of occlusioncaused by flaps in both coronary native vessels and by-pass grafts.Stents can also be used to reinforce collapsing structures in therespiratory, biliary, urological, and other tracts. For steps 20, 22 and24, FIG. 3 demonstrates a simple means for exposing tubular member 64 toa cleaning solution 60, coupling agent 61, or the photo-sensitive resist63 within a container 62. For example, Industroclean solvent detergentmade by Amway Corporation is an example of suitable commerciallyavailable cleaning solution. A number of organo-silane coupling agentsmay be employed with the current invention process. Some examples ofcommercially available organo-silane coupling agents arevinyltriethoxysilane or methyltriethoxysilane made by Union Carbide andZ-6040 (containing glycidoxypropyltrimethoxysilane) or Z-6020(containing aminoethylaminopropyltrimethoxysilane) made by Dow Corning.Probimide made by Olin Industries is an example of suitable commerciallyavailable photo-sensitive resist. When exposing the tubular member 64with some commercially available photosensitive resists 63, thethickness of the resist polymer layer is dependent upon the amount ofexposure time and possibly, the method of exposure or other variables.One method that can be employed to control the thickness of thephoto-sensitive resists is to uniformly draw the tubular member(s) 64through a solution of photo-resist for a specified period of time toobtain the desired coating layer. Furthermore, it may be desirable toprotect the internal lumen of the tubular member from thephoto-sensitive resist polymer during the exposure process.

[0045] It should be obvious to the one skilled in the art that standardmethods of subjecting one or more tubular members to a cleaning solutionare commercially available and can be employed with the presentinvention. In addition, it would be obvious to those skilled in the artto expose the cleaned tubular member to a heat source, preferably in thetemperature range of 100 to 200 degrees Celsius, to facilitate drying ofthe tubular member. Furthermore, it should be obvious to one skilled inthe art that standard methods of coating one or more tubular memberswith a coupling agent or photosensitive resist are commerciallyavailable and can be employed with the present invention. Having saidthis, subjecting tubular members of different metallic compositions mayrequire different commercially available photo-sensitive resists or, ifnecessary, coupling agents.

[0046]FIG. 4-A demonstrates a cross-section of the outer surface oftubular member 64 coated with a photo-sensitive resist 66. In thisexample, the adhesion properties between tubular member 64 and theresist 66 is robust enough to not require an intermediate coupling agentlayer. For example, using class 316 or 321 stainless steel for thetubular member with Probimide made by Olin Industries is an example of asuitable photo-sensitive resist/tubular member combination that does notneed a coupling agent. It should be recognized by the artisan that thereare several classes of polymers that can be employed with the presentinvention to function as a protective coating.

[0047]FIG. 4-B shows a cross-section of the outer surface of tubularmember 64 coated with a photo-sensitive resist 66. Sandwiched betweenthe tubular member 64 and resist 66 is a coupling agent 68. In thisexample, the adhesion properties requires the use of a coupling agent tofacilitate and strengthen the bond between the tubular member 64 and theresist 66. For example, using gold alloy or platinum metal for thetubular member with Probimide photo-sensitive resist is an example of acombination that may need an organo-silane coupling agent to strengthenthe bond between the tubular member and the resist.

[0048]FIGS. 5A and 5B show a preferred stent configuration imprinted ona transparent photographic film. The drawing of the pattern is generatedon a computer program, reduced and printed onto a transparent film. Forexample, a stress analysis program called ALGOR was used to develop thecomputer generated printouts. The printout is then sent to a filmprocessing facility who reduces the printout and generates a preciselydimensioned negative. As discussed in more detail below, the dimensionsof the negative must be calibrated to render a specific stent design.Because of regulations concerning patent drawings which prohibit largeblackened areas, an explanation of the drawings used to represent thephotographic film is necessary. In FIGS. 5A and 5B, the open(transparent) spaces which allow the UV light to pass through the filmare represented as solid black lines and alternating loops. The whiteareas of the drawings 5A and 5B represent the exposed (black) areas ofthe film which will block the UV light from passing through the film andexposing the underlying areas to UV. An example of a suitable film thatcan be employed in the present invention is Kodak ALI-4 Accumax filmmade by Kodak Industries. The length 77 of stent imprint is directlyequal (1 to 1) to the circumference of tubular member 64. The width 75is equivalent to the working length of the processed stent. FIG. 5Bshows the transparent photographic film 76 with multiple frames 70 ofthe preferred stent configuration.

[0049]FIG. 6 shows sections of the apparatus including the ultravioletlamp 82 laid-out in a typical configuration with sealed bulb 81 andfilament 80 in an assembly. A regulating platforms 84 comprises a base84 with a top plate 88. A specially configured slit 87 centers theultraviolet light into a narrow beam which reaches and penetrates thespecific pattern of transparent film 76. Selected portions of the coatedtubular member are illuminated with ultra-violet light which causes theexposed photo-resist to react and change its properties (cure andharden) and result in those portions remaining after electro-chemicaletching as the stent struts 118.

[0050] The platform also comprises a rotating member 86 engaged withtubular member 64. Rotating member 86 moves in conjunction with the filmpassing over the rotating tubular member.

[0051] For step 28, FIG. 7 demonstrates a simple means for exposingtubular member 92 to a negative resist developer 90, within a container94. It should be recognized by the artisan that there are numerouscommercially available solvents for selectively removing the unexposedphoto-sensitive resist of polymeric protective coating. It should alsobe obvious to the artisan that standard methods of exposing one or moretubular members with a negative resist developer can be employed.

[0052]FIG. 8 is a representation of step 30 where a means 100 is used toremove unexposed photo-sensitive resist or protective polymeric coatingand rinse excess negative resist developer or other selective solventsfrom the partially exposed tubular member 92 using an appropriatesolvent 102. In the preferred embodiment, QZ3501 made by Olin Industriesis an example of suitable commercially available solvent to rinse theexcess negative resist developer. At this time, the entire tubularmember is incubated for a specified period of time, allowing theremaining photo-sensitive resist polymer to fully cure (harden) andattach to the surface of the processed tubular member. The tubularmember can be incubated at room temperature or can be exposed to a heatsource in the range of 100 to 400 degrees Celsius.

[0053]FIG. 9 is a representation of step 32 where an electro-chemicalmeans is employed to remove the unexposed metallic material from theexposed tubular member 92. Shown in FIG. 9 is electro-chemical solution110 contained within a member 116. In the preferred embodiment, acombination of phosphoric acid and sulfuric acids are employed to theetch unexposed metallic material. Hydrite 4000 made by HydriteIndustries is an example of suitable commercially availableelectro-chemical etching solution that contains the phosphoric andsulfuric acids. When employing a tubular member composed of stainlesssteel class 304, the preferred electro-chemical etching solutioncomprises a solution of ferric chloride. If the tubular member iscomposed of a gold alloy or platinum, other electro-chemical etchingsolutions, such as potassium cyanide, aqua regia (hydrochloride andnitric acids), or sodium hypochlorite may be required. To energize theetchant solutions, a negative charge is supplied through cathode 112(which is immersed in the etchant solution) to the positively chargedelectrode 114 with is engaged to final tubular member 119 (of which bothare immersed in the etchant solutions). Materials commonly employed ascathodes are platinum or gold. It should be obvious to one skilled inthe art that standard methods of treating one or more tubular memberswith a electro-chemical means can be employed.

[0054]FIG. 10 is a representation of the preferred stent design 72 thatresults from the present invention method. The portions of thephotoresist that were exposed to UV illumination and changed physicalproperties (cured and hardened) are retained during the electrochemicalprocess and remain intact as the struts or loops 118 of stent 72. Theportions of the photoresist that were not exposed to UV illumination areremoved during the electrochemical process and result in open spaces120. The structure resulting from a pattern of struts 118 and openspaces 120 comprises the desired stent configuration. The presentinvention results in the preferred stent design 72 having specificallyconfigured struts 118. FIGS. 11, 12, and 13 illustrate, incross-section, three exemplary stent strut designs. As demonstrated inFIG. 11, the preferred stent design has the outer portion of the strutsprotruding in a trapezoidal configuration 134 which is directed radiallyfrom the longitudinal axis of the stent. The pattern of the preferredstent employs cross-section FIG. 11 and has a series of loops (U-shaped)118 and a single backbone running along the length of the stent, therebyforming the basic scaffold of the stent design.

[0055] The pattern of FIGS. 10 and 11 can be formed of any size; apreferable size is between 0.035 thousandths to 0.100 thousandths indiameter when formed (crimped). The expanded or deployed diameter rangesfrom 2.0 mm to 8.0 mm with a preferred range for coronary applicationsof 2.5 mm to 6.0 mm. The length of the stent is virtually constant fromits initial formation length to its length when expanded and ranges from2 mm to 50 mm, with a preferred length for coronary applications of 5 mmto 20 mm.

[0056] In an alternate embodiment, the pattern of stent 72 is similar tothat of FIGS. 10 and 11 but differs in the outer portion of the strutcomprising a triangular configuration 132 (FIG. 12) where the point ofthe triangle is directed radially from the longitudinal axis of thestent. In another alternate embodiment, the pattern of stent 72 issimilar to that of FIGS. 10 and 11 but differs in the outer portion ofthe strut comprising an extended base with a radius 130 (FIG. 13) whichis directly radially from the longitudinal axis of the stent.

[0057] Finally, the stent 72 can be polished to remove any excessmaterial not properly removed by the process. The polishing can beperformed mechanically, by rubbing a polishing stick having diamond duston its outside inside the stent 72. Alternatively, an additionalelectro-polishing step can be utilized.

[0058]FIG. 14 is a simplified perspective view of the apparatus used inthe present invention stent fabrication process. Mounted on a stage is asupporting means 141 for locating the enclosure 142 containing UV lightsource 82 over the Y shaped regulating platform 84. The UV light sourcehas a wavelength within the range of 360 to 440 nanometers with apreferred wavelength of 390 nanometers.

[0059] A series of repeating stent patterns or individual frames 70 areimprinted on a spool of film 147 which is engaged to rotating shaft 146.A motor 143 is engaged to and rotates the shaft 146 which speed isregulated by controller 140. Mounted also on the stage is regulatingplatform 84 which supports the coated tubular member 64 engaged to arotatable shaft 86. The top of the regulating platform comprises a platewhich is mounted within two horizontal inward facing slots cut intoregulating platform 84. The top contains a specifically configuredcentering slit 87 positioned over the film 76 and coated tubular member64. The function of the configured slit is to act as a slit lens andcenter the UV light obtained from the light source onto the narrowregion of the film. In this simplified example of the apparatus, thefilm engages the tubular member 64 which is free to rotate on shaft 86.The movement of the photographic film over the tubular member 64generates a rotational force which is in unison with the advancement ofthe film. An alternate method not shown would be to use a synchronizedmotor mechanism that would control both the advancement of the film andthe corresponding rotation of the tubular member. Also not shown is ameans to automatically remove the exposed tubular member 92 from theregulating platform and replacing with a coated tubular member 64. Theautomatic mechanism needs to correspond with the movement of the film toreplace the tubular member between individual stent patterns (frames)70.

[0060] Mounted on the side of the stage is another supporting means 154containing a rotatable shaft 150. A weight is suspended from the end ofthe photographic film 148 and functions to provide tension on thephotographic film to ensure adequate engagement with coated tubularmember 64. A take-up reel or any number of tensioning mechanisms cansuffice for the weight 148.

[0061]FIG. 15 is a cross-sectional view of the apparatus as seen alongline 2—2 in FIG. 14 showing the perspective view of the apparatus. Thiscross-sectional view shows the relative position of UV light source 82over regulating platform 84, slit 87 and tubular member 64. It can beseen from this figure that weight 148 provides tension to maintain theengagement of the photographic film to the tubular member.

[0062]FIG. 16 is a cross-sectional view of the light source and theregulating platform. This view demonstrates the orientation of the lightsource 82 facing in the general direction of the regulating platform 84.Diffuse UV light (shown by the arrows emanating from the light source)enter into specially configured slit 87. The figure also demonstratesone embodiment of the apparatus where the forward advancement of thephotographic film 76 (shown by arrow) generates a rotational force(shown as clockwise) on the coated tubular member 64 which moves inunison with the film.

[0063]FIG. 17 is a cross-sectional enlargement of the regulatingplatform of the apparatus, specifically demonstrating the configurationof the focusing slit 87. Light enters beveled angles 90 which funnelsthe electromagnetic energy into a narrow channel 92 finally engagingphotographic film 76. The pattern imprinted on the film blocks some ofthe light rays; while spaces in the pattern allow light to reach andreact with the photo-sensitive resist on the coated tubular member 64.This process transfers the stent pattern from the relatively flatphotographic film to the circular tubular member.

[0064]FIG. 18 is a side perspective view of the regulating platform.This figure shows a section of regulating platform 84, depicting one ofthe beveled angles 90 and one side of the narrow channel 92 of slit 87.Also demonstrated is that the width of beveled angle 90 and channel 92is approximately equivalent to the width of the photographic film 76.Also shown is the photographic film 76 engaged with coated tubularmember 64. Length 77 of frame 70 is designed and calibrated to equal thecircumference of tubular member 64.

[0065] It is to be appreciated by persons skilled in the art that thepresent invention is not limited to what has been particularly shown anddescribed hereinabove. Rather the scope of the present invention isdefined only by the claims which follow:

1. An apparatus for imprinting a stent configuration image from a maskform onto a tubular stent blank, the stent blank having a longitudinalaxis and a photosensitive coating on the outer surface thereof, theapparatus comprising: a journaling mechanism adapted to receive thestent blank, and operable to rotate the stent blank about itslongitudinal axis; a radiation source operable to direct light at afirst surface region of the stent blank when mounted in the journalingmechanism, to thereby expose the photosensitive coating on said firstsurface region of the stent blank; and a mask form movement mechanismconfigured to mount the mask form in the apparatus and to move the maskform along a path in which the mask form contacts the stent blank insaid first surface region thereof along a concurrent convex arcuatesegment.
 2. An apparatus as in claim 1 wherein the mask form movementmechanism comprises a film take-up reel.
 3. An apparatus as in claim 1wherein the mask form movement mechanism comprises a synchrono-gearedmechanism operable to synchronously move the film along the film pathand to rotate the stent blank around its longitudinal axis.
 4. Anapparatus as in claim 1 further comprising a slit mechanism whichshields the stent blank from exposure to radiation from said radiationsource except in said first surface region.
 5. An apparatus as in claim1 further comprising a mask tensioning apparatus which is operable totension the mask form against the stent blank along said concurrentconvex arcuate segment.
 6. An apparatus as in claim 5 wherein a motor isprovided which is operable to drive rotation of the stent blank and toconcurrently drive movement of the mask form along said path.
 7. Anapparatus as in claim 6 wherein the motor is associated with the maskform movement mechanism to drive movement of the mask form, the maskform movement driving rotation of the stent bank.
 8. An apparatus as inclaim 1 wherein the radiation source is a UV light source.